Magnetic Particle Spectroscopy for Detecting Cell-Associated Zinc Ferrite Nanoparticles and Probing Their Relaxation Dynamics
Abstract
Magnetic particle spectroscopy (MPS) enables sensitive detection of magnetic nanoparticles (MNPs) and characterization of their dynamic magnetization through higher-order harmonics. Here, we synthesized citrate-functionalized, 30 nm cubic Zn0.4Fe2.6O4 (ZFO) MNPs and investigated their association with SKOV3 ovarian cancer cells using MPS. The ZFO MNPs exhibited a crystalline spinel structure, a mean hydrodynamic diameter of 39.4 nm, strong room-temperature magnetization, low coercivity, and citrate-associated surface functional groups. Live/Dead imaging indicated good cytocompatibility after 24 h exposure at concentrations up to 0.5 mg/mL, while bright-field microscopy showed concentration-dependent cell-associated nanoparticle accumulation. Two MPS drive fields were compared using ZFO MNPs dispersed in DI water and agar as relatively unrestricted and strongly confined reference states. The 7.75 kHz, 20 mT condition retained more higher-order harmonics than 11.37 kHz and 10 mT and produced a larger and order-dependent spectral separation between the two states; it was therefore selected for the cellular measurements. After ZFO exposure and removal of unbound nanoparticles, MPS detected cell-associated MNPs in samples containing 0.1, 1, and 2x10^6 SKOV3 cells. The 3rd-, 5th-, and 7th-harmonic amplitudes increased proportionally with cell number, with power-law exponents of 1.03-1.09. We also report that most normalized harmonic ratios from the 1- and 2x10^6-cell samples fell between the water and agar references, indicating partial restriction of Brownian rotation in the cellular environment. These findings demonstrate that MPS can detect cell-associated MNPs while providing complementary spectral information about their ensemble-averaged physical confinement, supporting its application in magnetic cell labeling and cell-tracking studies.
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BibTeX
@misc{wang2026magnetic,
title = {{Magnetic Particle Spectroscopy for Detecting Cell-Associated Zinc Ferrite Nanoparticles and Probing Their Relaxation Dynamics}},
author = {Hanlei Wang and Bahareh Rezaei and Md Shahriar and Changxue Xu and Rui He and Kai Wu},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.14162},
eprint = {2609.14162},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.14162},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Magnetic Particle Spectroscopy for Detecting Cell-Associated Zinc Ferrite Nanoparticles and Probing Their Relaxation Dynamics
AU - Hanlei Wang
AU - Bahareh Rezaei
AU - Md Shahriar
AU - Changxue Xu
AU - Rui He
AU - Kai Wu
PY - 2026
DA - 2026/09/12
PB - arXiv
DO - 10.48550/arxiv.2609.14162
UR - https://arxiv.org/abs/2609.14162
AB - Magnetic particle spectroscopy (MPS) enables sensitive detection of magnetic nanoparticles (MNPs) and characterization of their dynamic magnetization through higher-order harmonics. Here, we synthesized citrate-functionalized, 30 nm cubic Zn0.4Fe2.6O4 (ZFO) MNPs and investigated their association with SKOV3 ovarian cancer cells using MPS. The ZFO MNPs exhibited a crystalline spinel structure, a mean hydrodynamic diameter of 39.4 nm, strong room-temperature magnetization, low coercivity, and citrate-associated surface functional groups. Live/Dead imaging indicated good cytocompatibility after 24 h exposure at concentrations up to 0.5 mg/mL, while bright-field microscopy showed concentration-dependent cell-associated nanoparticle accumulation. Two MPS drive fields were compared using ZFO MNPs dispersed in DI water and agar as relatively unrestricted and strongly confined reference states. The 7.75 kHz, 20 mT condition retained more higher-order harmonics than 11.37 kHz and 10 mT and produced a larger and order-dependent spectral separation between the two states; it was therefore selected for the cellular measurements. After ZFO exposure and removal of unbound nanoparticles, MPS detected cell-associated MNPs in samples containing 0.1, 1, and 2x10^6 SKOV3 cells. The 3rd-, 5th-, and 7th-harmonic amplitudes increased proportionally with cell number, with power-law exponents of 1.03-1.09. We also report that most normalized harmonic ratios from the 1- and 2x10^6-cell samples fell between the water and agar references, indicating partial restriction of Brownian rotation in the cellular environment. These findings demonstrate that MPS can detect cell-associated MNPs while providing complementary spectral information about their ensemble-averaged physical confinement, supporting its application in magnetic cell labeling and cell-tracking studies.
ER -